1. Field of the Invention
The present invention relates to an applicator for direct or indirect application of a liquid or pasty medium onto a traveling fiber material web.
2. Description of the Related Art
In the case of direct application, the applied medium is transferred directly onto the traveling fiber material web, notably of paper or cardboard. In indirect application, the applied medium is first transferred to an applicator roll, which in turn transfers the applied coating medium onto the fiber material web.
There are prior applicators wherein two lips form between themselves a metering slot which acts as an open-jet nozzle. The metering slot is also called a color discharge slot. Such an applicator can be described as an open-jet nozzle applicator or "Fountain Applicator" (JetFlow F), due to the formation of an open jet of the liquid or pasty medium proceeding through the ambient atmosphere. The liquid or pasty medium is applied by the open jet directly or indirectly onto the traveling material web.
In general, in this applicator the liquid or pasty medium is fed via a color manifold which is arranged within a support beam extending across the width of the applicator (or the width of the web being coated). The medium proceeds from the color manifold via conduits in an equalization space and flows from there via a feed conduit to the metering slot, from which the liquid or pasty medium subsequently exits in the form of the "open jet." In the direct application of the medium, a material web passes by the open-jet nozzle and is acted upon, as described above, directly with the open jet of the liquid or pasty medium. The material web can in the process be carried, for example, on the surface of a roll. In the indirect application of the medium, the open jet is applied first on a substrate, e.g., the surface of an applicator roll, and transfers from the applicator roll to the material web in a nip through which the material web passes.
Of the two lips forming the metering slot, the one disposed on the side of the metering slot on which the fiber web approaches the applicator is termed the approach-side lip. Accordingly, the second lip, disposed on the side of the metering slot on which the fiber web departs from the applicator, is termed the departure-side lip.
The open-jet nozzle applicator is usually followed by a final metering system which by use of a doctor element, e.g., a doctor blade, scrapes the applied liquid or pasty medium down to the desired amount of application. Arranged between the departure-side lip of the applicator and the final metering system, furthermore, is a collection trough serving to collect surplus liquid or pasty medium draining from the applicator or from the final metering system.
Such an open-jet applicator is known, for example, from U.S. Pat. No. 5,436,030 or DE 44 32 177A1.